The purpose of the proposed research is to develop an animal model for human depression based upon Pavlovian experimental neurosis in cats. The procedure for the proposed research is basically an adaptation of the Pavlovian method of increasingly difficult discrimination to an instrumental learning situation where the effects of the neurosis may be more precisely quantified. Our data to present suggest that when a discrimination begins easy, but is made more and more difficult, the animal ceases performing in the situation and manifests a variety of collateral symptoms which may be characterized as lethargy, lack of behavior initiation and a general motivational deficit. The basic objectives of this research are to attempt to assess the validity of experimental neurosis as a model of depression in three general ways: 1) to determine the generality of the amotivational state produced by experimental neurosis to a variety of different situations -- human depression being characterized as a general loss of "positive motivation," 2) to compare the effects of antidepressant drugs in this syndrome with known human clinical effects, 3) to examine in detail the parameters affecting the production of experimental neurosis in order to provide a basis for understanding the etiology of depression.